If you wish to undertake charitable street collections on the street you should contact the Metropolitan Police.
If you wish to hand out leaflets on the street you may do so provided you do not cause an obstruction to the public highway and you do not cause a nuisance, littering for example.
Ice cream vans
Ice cream vans are exempt from needing a street trading licence provided you are trading from a vehicle which goes from place to place remaining in any one location in the course of trading for periods of 15 minutes or less and not returning to the same location or any other location in the same street on the same day.
Busking is neither licenced nor prohibited within the London Borough of Barnet. Therefore, you may busk on the public highway provided you do not cause a nuisance.